The Hated Black Mage Returns summary:

Kai, a black mage, is betrayed by his brother, the brave Ares, and killed along with the demon lord. Ares, the brave, was about to take possession of Collette, the saint who loved Kai.However, Kai, who was just killed by Ares, suddenly woke up and found that time had returned until the day of the [class revelation ceremony] five years ago. Kai knowing the future of receiving the class "Black Mage" and being despised for incompetence and expelled from the aristocracy, with the dark power of level 999 that he took over from his first time, he decided to overthrew the brave Ares and took back his childhood friend, the saint Collette to change the fate of destruction.A revenge story of the hated who takes back his loved ones and changes the future begins!